Patent GB-546881-A (GB)
Title: Improvements in or relating to depth of focus indicators for photographic cameras
IPC: G03B17/02
Filed: 1941-12-30
Abstract: 546,881. Depth of focus indicators for photographic cameras. KODAK, Ltd. Dec. 30, 1941, No. 16799. Convention date, June 7. [Class 98 (i)] A camera is provided with a depth of focus indicator in combination with an objective focusing mechanism and a diaphragm operating member, the relative positions of the indicator and a focusing scale being automatically adjusted by the adjustment of the diaphragm operating member and the focusing mechanism, whereby the depth of focus is directly indicated in accordance with the diaphragm setting and the focal adjustment. As in the form described, the depth of focus indicator may be adjusted transversely of the focusing scale on operation of the diaphragm adjusting member. In this form the depth of focus indicator is carried by a lens mount in conjunction with a rotary focusing scale. The mount comprises a stationary supporting sleeve 17 which is attached to the camera body by a threaded ring 24 rotatably carried by the latter, and is formed with a recess in which is threaded a locating ring 19 having a slot engaged by a locating pin 22 on the camera body, the ring 19 being staked in position after it has been adjusted with the slot in the correct position. A focusing ring 28 threaded on the stationary sleeve 17 rotates a focusing tube 30 through a key 31 engaging an axial slot 33 in the latter. The tube 30 is prevented from axial movement by a key 35 engaging a circumferential groove in it, and is in threaded engagement with the lens barrel 12, which is thereby moved longitudinally. A diaphragm operating ring 40 is threaded on to the lens barrel at 41 and is connected by a screw 45 to the rotatable ring 16 of the diaphragm. The focusing scale 48, Fig. 4, is carried by a ring 50 which is caused to rotate with the focusing ring 28 through a pin and slot connection 51, 52, and to move axially with the ring 40 by a pin and slot connection 63, 64. When the threads between the focusing ring 28 and sleeve 17, and the focusing tube 30 and lens barrel 12 are of the same pitch, the ring 50 may be formed as an extension of the ring 28, instead of as a separate member, since its axial movement and that of the ring 40 will then be equal. Between the rings 40 and 50 is a depth of focus ring 55, shown separately in Fig. 5. This ring is moved axially on rotation of the diaphragm ring 40 by means of pins 62 on the latter engaging in cam slots 61, and is prohibited from rotational movement by pins (not shown) extending from the lens barrel 12 into axial slots 58. The axial movement of the ring 55 causes a portion of the ring formed with splayed edges 56, 561 and carrying an index mark 57 for the focusing scale, to project more or less beyond the edge of the ring 50, the form of these edges and that of the cam slots 61 being such that their points of intersection with the edge of the scale 48 indicate the limits of the field of focus for each setting of the diaphragm. In a modification, the edges 56, 561 are stepped, each step corresponding to a diaphragm setting. In alternative forms, the ring 55 may be of uniform width, with index lines corresponding to the edges 56, 56<SP>1</SP> marked on it, in which case it may be of transparent material and overlie the ring 50. When not carried by the lens mount, the focusing and depth of focus scales may be flat and in overlapping relation, the former being moved in the direction of its length by a connection to the focusing mechanism and the latter being moved transversely to this direction by a connection to the diaphragm adjusting mechanism.